1. Field of the Invention
The present invention relates to image processing, more specifically, to a method and system for describing an image region based on color histogram, a method and system for registering an object from one or more images, and a method and system for detecting an object from an image based on the registration.
2. Description of the Related Art
Image description technique is a basis for content-based image detection or content-based image retrieval. Since the visual feature of an image extracted automatically by a computer is dramatically different from the image content sensed by a human, the image description technique is needed for the computer to extract features from the image, which can be processed and used by the computer to distinguish one image from others.
In the prior art, traditional low-level visual features such as color, texture, shape and etc. can be used for image description. However, this invention mainly focuses on image description based on color information.
Image description based on color information is useful in a number of applications such as digital image libraries wherein the image description is used as a basis for image indexing and retrieval.
For the image description to be practical and effective, the outcome of extracting features (color information) from the image should be: (1) sufficient to distinguish between different images, (2) invariant to certain types of transformations of image, (3) insensitive to noise, (4) easy to compute.
However, image description based on color information is rarely applied to object detection, because the color feature is usually disturbed by many factors, such as light source, photosensitive devices of camera and etc. For example, in the image description method using color information as image feature as disclosed in US application published as U.S. Pat. No. 6,850,639, the color feature is disturbed by lighting and parameters setting (white balance, focal length, etc.) of camera. The same objects in images captured in different lighting or with different camera settings might not be distinguished from each other.
Therefore, there is a need for a technique that is capable of precisely describing an image region based on color information without being largely affected by lighting, camera setting and etc. Based on the image description technique of the present invention that are less affected by lighting, camera setting and etc., naturally, a high detection precision will be obtained.